Richardson's handbook of projection (1930)

MANAGERS AND PROJECTIONISTS 1051 been in one position (not turning) for quite some while. Examine the surface of the chute the film passes through in its exit from the upper magazine, making certain that its surface is smooth and free from all deposit. Films have been badly injured by deposits occurring here. Not all projectors have such a chute. Passing on down, it is well to carefully examine all sprockets and sprocket idlers to make certain the faces of the sprockets are perfectly clean — particularly the intermittent and sound sprockets. If there is any deposit, a good stiff toothbrush is best to clean it off with. If it be dampened with kerosene the deposit will come off more readily. Give the idler rollers a drop of thin oil once each day. Continuing down, examine the sound sprocket with particular care, because any deposit on its face will throw it out of round and create a more or less objectionable effect upon the sound reproduction, according to the depth of the deposit. This sprocket should be carefully examined at least once a day. Because you find no deposit for some while, either in the gate or on the sound sprocket, don't get careless. If you do you may suddenly find yourself with a reel of film ruined on your hands. In addition to what has been set forth, the fire trap rollers of the lower magazine must be examined each day, and any and all other places where the film does or may rub against metal in its passage through the projector and sound reproducing mechanism. SOUND GATE APERTURE.— Keep it perfectly clean. Dirt or dust in it will reduce sound volume and injure its quality.